The present invention relates to a workpiece fabric holding device. The present invention also relates to a pocket setter having a workpiece fabric holding device.
An automatic pocket setter unit has been proposed in U.S. Pat. No. 4,883,006 for automatically sewing a pocket to a garment. In this unit, edge portions of a pocket cloth are folded by a pocket folding means, and the folded edge portions are stitched to the garment.
More specifically, as shown in FIG. 10, the pocket setter unit includes a sewing machine 101 for performing a stitching operation, a sewing machine table 102, a work-piece fabric holding/feeding unit 103 for pressedly holding a workpiece or a pocket cloth W onto the sewing machine table 102, a pocket folder 104 for folding edge portions of the pocket cloth W and for mounting the pocket cloth onto a garment, and a stacker 105 for successively stacking stitched pocket cloths and the garments. The sewing machine table 102 serves as a working table available for both the pocket folder 104 and the sewing machine 101 as well as for a throat plate therefor.
The sewing machine 101 described is movable in the Y-direction by a moving mechanism which includes a Y-axis servo motor (not shown in FIG. 10) and a toothed belt 112. The workpiece fabric holding/feeding unit 103 includes a pressure plate 114 formed with a slit-like needle cut-out 113, and a feed arm 115 to which the pressure plate 114 is attached. A second moving mechanism is provided for moving the feed arm 115 in X-direction. The second moving mechanism includes an X-axis servo motor 116 and a toothed belt 117. Further, the feed arm 115 is supported on a slider member 118 movable in a vertical direction. The slider member 118 is connected to a pneumatic cylinder 119 whose cylinder rod is vertically extendible and retractable, so that the feed arm 115 is movable in a vertical direction. Consequently, the pressure plate 114 has a descent position in which the plate 114 is pressingly positioned on the sewing machine table 102, and an ascent position in which the plate 114 is moved away from the sewing machine table 102.
The pocket cloth whose edges are folded by the pocket folder 104 is mounted on the garment mounted on the sewing machine table 102. Then, the pocket folder 104 is moved upwardly, and the workpiece holding/feeding unit 103 is moved so as to press the workpieces W (including the pocket cloth and the garment) onto the sewing machine table 102 by the pressure plate 114. Thereafter, the workpiece holding/feeding unit 103 moves, the workpieces W slidingly on table 102 from a pocket folder position to the sewing machine position. By controlling the movements of the sewing machine 101 and the workpiece fabric holding/feeding unit 103, a sewing locus for performing a pocket stitching is provided along the needle cut-out 113 formed on the pressure plate 114 for performing a pocket stitching.
In this type of automatic sewing machine, the work-pieces W including the pocket cloth and the garment are stackedly pressed on the sewing machine table 102, and the workpiece fabric holding/feeding unit 103 moves the work-pieces W to the intended needle location for moving the workpieces W along the sewing locus. As described in the above U.S. Pat. No. 4,883,006, the workpiece fabric holding/feeding unit 103 is provided with the pressure plate 114. A thin needle slot or cut-out is formed in the pressure plate 114. The thin needle slot or cut-out has a configuration in conformance with the sewing locus.
In this case, if the sewing locus is of a single array, the above described pressure plate 114 is available for performing its inherent function. However, if sewing must be made along two arrays of sewing loci 3 and 4 as shown in FIG. 9, it would be almost impossible to press a portion adjacent the sewing loci 3 and 4 with using the pressure plate 114 formed by the simple needle slot 113.
In this connection. U.S. Pat. No. 3,930,454 discloses a workpiece fabric holding device capable of performing two arrayed sewing. According to the disclosed device, three pieces of movable plates are prepared for pressing an inner side of a pocket cloth 2, and these movable plates are moved by pneumatic cylinders. In case of sewing along an outer sewing locus 3, the movable plate is positioned in a vicinity of an edge portion of a stationary plate for pressing the outer side of the pocket cloth 2, so that a thin needle slot corresponding to the outer sewing locus 3 is formed. In case of sewing along an inner sewing locus 4, the movable plates are retracted so as to form a wide needle slot, and the movable plates press inner side of the inner sewing locus 4.
However, in the above described conventional device, when sewing along the inner sewing locus 4, a large distance is provided between the movable plates and the stationary plate, and the stationary plate presses a portion of workpiece W spaced away from the inner sewing locus 4. On the other hand, when sewing along the outer sewing locus 3, the three pieces of the movable plates are outwardly projected, so that gaps are provided between the neighboring movable plates. The gap portion cannot press against the pocket cloth portion which is the inner side portion with respect to the outer sewing locus 3.
Therefore, the conventional device may be only available for sewing a thick cloth such as jeans, but the device does not appear to be available for sewing a thin cloth. That is, n the latter case, the thin workpiece fabric may become jumped or corrugated in response to every penetration of the sewing needle therethrough, and a hook of a shuttle race body may fail to catch the thread, to thereby causing skip stitches and thread breakage.
Further, according to the conventional device, the movable plates are moved while maintaining pressure to the workpiece fabrics i.e., a garment 1 and the pocket cloth 2. Therefore, the garment 1 and the pocket cloth 2 may be displaced relative to each other. Specifically, regarding the thin cloth, the folded edge portion of the pocket cloth 2 may become displaced or deviated during the movements of the movable plates. To avoid these drawbacks, the bottom surfaces of the movable plates are not provided with elastic members such as sponges, but their bare metal surfaces are exposed to reduce sliding resistance with respect to the workpiece fabrics 1 and 2. Still however, the workpiece holding performance may still be degraded, if the entire workpiece fabrics 1 and 2 are slidably moved on the sewing machine table 102 by the workpiece fabric holding device, because the relative displacement between the garment 1 and the pocket cloth 2 may occur at the pressing portions given by the movable plates.
In another conventional workpiece fabric holding device, the entire device is lifted together with the stationary plate so as to move the movable plates. With this structure, a negative pressure suction means is be required to avoid displacement of the workpiece fabrics on the sewing machine table during the lifting of the holding device. Consequently, the resultant device becomes much more intricate and costly.